A Comparative Study of Global Transcriptomic Responses under Excess or deficient Phosphate (Pi) Regime reveals ethylene mediated signaling in Arabidopsis.

Phosphorus is an essential macronutrient element, but some time causes problems if present in excess. Unlike the enormous molecular and morphophysiological information available in plants regarding phosphate (Pi) deficiency, little is known about the effect of excess Pi on plants, which is indeed essential for its remediation. Here, we have carried out a comparative study of plant molecular responses under excess Pi (20 mM) or without Pi (0 mM) at transcriptome level. The 1.25 mM treatment concentration of Pi used as a control to obtain differentially regulated genes under above mentioned Pi regimes. A novel whole-transcript expression array, i.e. Arabidopsis Gene 1.0 ST Array, was used to perform these experiments. The most distinctly regulated groups of genes represent modulation in ethylene mediated signaling, Fe deficiency response, and root development. We have also identified some defensin like genes, possessing a gibberellic acid regulated domain (GASA like) under excess Pi treatment. Overall, this study will not only help in dissecting the mechanism of plant responses under excess Pi but also provide the clues about the unknown genes involved in phosphorus homeostasis. A total of eighteen (18) samples with biological triplicates under two tissue types (root and shoot) and three phosphorus treatment conditions. The treatment groups consist of: (1) root and shoot with 1.25 mM phosporus treatment (control); (2) root and shoot with 20mM phosphorus treatment; and (3) root and shoot without phosporus treatment (P-).